This invention relates to a sight flow indication apparatus, and particularly to a kind of sight flow indication apparatus having a plurality of protective arrangements respectively provided therewith so as to ensure that no oozing or leakage of the liquid material contained therein will occur when an unexpected deficiency is caused thereto.
In a petrochemical industry or other chemical engineering facilities where great amounts of liquid products have to be processed, piping arrangements are usually provided to transfer the liquid products therefrom. In order to clearly understand whether the flow of the liquid products in the piping arrangements is normal or abnormal, or is cut off, and to ensure regular operations and prevent accidental injuries and/or damages, sight flow indicators, which are generally formed from a transparent glass tube, are respectively installed at an important and a clear portion of the piping arrangements for performing routine visual checks thereat. A conventional sight flow indicator is shown in FIG. 1. this indicator has the following defects:
(a) The glass tube 1 of a conventional sight flow indicator "A" is tightly secured between two flanged joints 2 by a pair of lock bolts 3 which are screw-fastened at the lower flange 2a of both flanged joints 2. Since the horizontal plane at the opposing ends of the glass tube 1 are neither evenly flat nor absolutely parallel, an end-seal gasket 11 is normally provided between the opposing end planes of the glass tube 1 and the annular surfaces of the lower flanges 2a. After a certain duration, however, leakage, contamination and even public hazards may occur due to the corrosion and infiltration of the chemical liquid through the end-seal gaskets 11.
(b) In order to obtain a premium tight connection between the tube 1 and the lower flanges 2a, the lock bolts 3 are fastened to the utmost limit of tension thereof through the nuts 31. Since the end-seal gaskets 11 are tightly pressed by the ends of the glass tubes 1, there is no leeway for the expansion and contraction of for the glass tubes 1 under hot and cold conditions. As a result, the edges of the glass tubes 1 often crack under high pressure, causing the chemical liquid in the glass tubes 1 to ooze out of the cracks therein. On the other hand, in order to avoid the cracking of the glass tubes 1 as mentioned above, the method of loosely fastening glass tubes 1 at both ends thereof is used, creating a clearance between the end surface of the glass tubes 1 and the end-seal gaskets 11. However, with this method, due to the surge pressure of the flowing liquid in the glass tubes 1, oozing or leakage of said liquid may occur from the clearance. If the liquid in the glass tubes 1 is poisonous, a very dangerous situation would result.